Python TKinter connect variable to entry widget

Question

Hi everyone,

I'm trying to associate a variable with a Tkinter entry widget, in a way that:

1. Whenever I change the value (the "content") of the entry, mainly by typing something into it, the variable automatically gets assigned the value of what I've typed. Without me having to push a button "Update value " or something like that first.
2. Whenever the variable gets changed (by some other part of the programm), I want the entry value displayed to be adjusted automatically. I believe that this could work via the textvariable.

I read the example on http://effbot.org/tkinterbook/entry.htm, but it is not exactly helping me for what I have in mind. I have a feeling that there is a way of ensuring the first condition with using entry's "validate". Any ideas?

Thank you for your input!
Sano

Answer 1

You want to bind a function to keypress event for the field as explained here, namely the <Key> event.

Answer 2

I think you want something like this, in the example below I create a variable myvar and assign it to be textvariable of both a label and entry widget, that way both are coupled and change in entry widget will reflect automatically in label

You can also set trace(http://effbot.org/tkinterbook/variable.htm) on variables, e.g. to write to stdout

from Tkinter import *
root = Tk()
root.title("MyApp")

myvar = StringVar()
def mywarWritten(*args):
    print "mywarWritten",myvar.get()

myvar.trace("w", mywarWritten)

label = Label(root, textvariable=myvar)
label.grid(sticky=W)
label.pack()

text_entry = Entry(root, textvariable=myvar)
text_entry.grid(column=0,row=1, sticky=W)
text_entry.pack()

root.mainloop()